B08_24R0030_Attachment_12_-_Bonita_Creek_Road_Geotechnical_Eval_0004.pdf

Geotechnical Evaluation

Bonita Creek Roadway Improvements

Graham County, Arizona

GLHN Architects & Engineers, Inc.

2939 East Broadway Boulevard | Tucson, Arizona 85716

January 12, 2023 | Project No. 607468001

Geotechnical | Environmental | Construction Inspection & Testing | Forensic Engineering & Expert Witness

Geophysics | Engineering Geology | Laboratory Testing | Industrial Hygiene | Occupational Safety | Air Quality | GIS

1991 East Ajo Way, Suite 145 | Tucson, Arizona 85713 | p. 520.577.7600 | www.ninyoandmoore.com

Geotechnical Evaluation

Bonita Creek Roadway Improvements

Graham County, Arizona

Ms. Donna Mertes, PE, LEED AP

GLHN Architects & Engineers, Inc.

2939 East Broadway Boulevard | Tucson, Arizona 85716

January 12, 2023 | Project No. 607468001

MJK/SDN/FFN/jom

Patrick M. Wundrock Staff Engineer

Marek J. Kasztalski Principal Engineer

Steven D. Nowaczyk, PE Managing Principal Engineer http://www.ninyoandmoore.com/

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 i

CONTENTS

1 INTRODUCTION 1

2 SCOPE OF SERVICES 1

3 SITE DESCRIPTION 1

4 TOPOGRAPHIC MAP AND AERIAL PHOTOGRAPH REVIEW 2

5 PROJECT DESCRIPTION 3

6 FIELD EXPLORATION AND LABORATORY TESTING 3

7 GEOLOGY AND SUBSURFACE CONDITIONS 4

7.1 Subsurface Conditions 5

7.1.1 Roadway Pavement 6

7.1.2 Alluvium/Residuum 6

7.1.3 Formational Material (Conglomerate) 6

7.2 Groundwater 6

8 GEOLOGIC HAZARDS 6

8.1 Land Subsidence and Earth Fissures 6

8.2 Faulting and Seismicity 7

9 CONCLUSIONS 8

10 RECOMMENDATIONS 8

10.1 Earthwork 9

10.1.1 Site Preparation 9

10.1.2 Excavations 9

10.1.3 Fill Materials and Reuse of On-site Soils 10

10.1.4 Subgrade Preparation 10

10.1.5 New Embankment Fill 11

10.1.6 Permanent Slopes 12

10.1.7 Special Slope Erosion Control Techniques 12

10.2 Seismic Design Considerations 13

10.3 Slab-On-Grade 13

10.4 Pavements 14

10.5 Corrosion 14

10.6 Concrete 15

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 ii

11 SITE DRAINAGE 15

12 CONSTRUCTION OBSERVATION AND TESTING 15

13 LIMITATIONS 16

14 REFERENCES 18

TABLES

1 – USDA Soil Units 5

2 – International Building Code Seismic Design Criteria 13

FIGURES

1 – Site Location

2A and 2B– Exploration Locations

APPENDICES

A – Boring and Test Pit Logs

B – Laboratory Testing

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 1

1 INTRODUCTION

In accordance with our proposal dated October 19, 2022, and your authorization, we have performed a geotechnical evaluation for the design and construction of proposed improvements along Bonita Creek Road in Graham County, Arizona (Figure 1). The purpose of our evaluation was to assess the subsurface conditions at the project site in order to provide geotechnical recommendations for design and construction. This report presents the results of our evaluation and our geotechnical conclusions and recommendations regarding the proposed construction.

2 SCOPE OF SERVICES

The scope of our services for this project generally included:

• Reviewing available topographic information, soil surveys, geologic literature, and aerial photographs of the project area.

• Conducting a visual reconnaissance of the project area and marking out the exploration locations.

• Notifying the Arizona 811 of the proposed exploration locations prior to conducting our field work.

• Drilling, logging, and sampling four exploratory soil borings to approximate depths ranging from approximately 4.4 to 8.9 feet below ground surface (bgs). The boring logs are presented in Appendix A.

• Excavation, logging, and sampling two exploratory test pits to approximate depth of 2 feet bgs. The test pit logs are presented in Appendix A.

• Performing laboratory tests on selected samples collected from our exploration locations to evaluate the in-situ moisture content and dry density, gradation, Atterberg limits, and corrosivity characteristics (including pH, minimum electrical resistivity, and soluble sulfate and chloride contents). The results of the laboratory tests are included in Appendix B.

• Preparing this report presenting our findings, conclusions, and recommendations regarding the proposed design and construction.

Our scope of services did not include environmental consulting services such as hazardous waste sampling or analytical testing at the site. A detailed scope of services and estimated fee for such services can be provided upon request.

3 SITE DESCRIPTION

Bonita Creek Road is a two-lane, chip sealed roadway located in Graham County, Arizona, that is situated approximately 15 miles northeast the City of Safford. This approximately 3-mile long roadway segment under study extends from East Sanchez Road to the Riverview Campground

Road as depicted on Figure 1. It provides access to Bonita Creek, the Gila River, the Gila Box

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 2

Riparian Conservation Area (GBRCA) and surrounding areas. The roadway also provides access to various recreational sites and amenities administered by the Bureau of Land

Management (BLM). These recreational sites are spread across the nature preserve’s riparian ecosystem that is located on approximately 23,000 acres of land administered by the BLM.

Several washes run in a northwest to southeast direction within the general project area. At the time of our evaluation, the project area included six major wash crossings along the roadway segment under study. The wash crossing consisted of low-water crossings with concrete slabs at three locations, galvanized steel pipe culverts at two locations and no improvements at one crossing. The project area was surrounded by mostly undeveloped desert land, rolling hills with sparse desert vegetation, and was adjacent to perennial washes with riparian vegetation and sandy beaches.

The Gila River was located within an average distance of 500 feet of the project alignment and the Coronado Trail (State Highway 191) was located approximately 5 miles southeast of the project areas. According to United States Geological Survey (USGS) stream monitoring site number 09448500, at the time of our evaluation the Gila River had a streamflow rate of approximately 800 cubic feet per second.

4 TOPOGRAPHIC MAP AND AERIAL PHOTOGRAPH REVIEW

According to the Gila Box Quadrangle, Arizona – Graham County, 7.5-Minute United States

Geological Survey (USGS) Topographic Quadrangle Map (2021) the ground elevations along the project alignment vary between approximately 3,160 feet relative to mean sea level (MSL) and 3,240 feet MSL. The topography of the area adjacent to the project alignment slopes gently from northwest to southeast towards the Gila River.

Several historical aerial photographs from Historicaerials.com (Nationwide Environmental Title

Research [NETR]) and from Google Earth™ were reviewed for this project. Aerial images dated

1983 through 1984 depicted the Bonita Creek Road as an unpaved roadway and no other developments within the project area. A 1998 image showed development of recreational day-time use sites and campsites along Bonita Creek Road. An image dated 2005 depicted low water concrete slab drainage crossings and short paved sections along Bonita Creek Road.

Aerials dated 2015 and later depicted Bonita Creek Road as a paved roadway and the project site similar to their current condition.

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 3

5 PROJECT DESCRIPTION

We understand that the BLM is considering improvements to the Bonita Creek Road segment under study to increase the longevity of the roadway and to confirm that consistent access is provided to the GBRCA recreational day-time use sites, campgrounds, and the City of Safford

Water facilities. The roadway segment; which is a popular destination for off highway vehicle users, hikers and rafters, has been reported to experience debris blockages at major drainage crossings during monsoon seasons that restrict access to utility facilities supplying the City of

Safford. In addition, drainage runoffs were observed to spill over the roadway at some locations leading to erosion on the downstream side of the roadway. When traveling on Bonita Creek

Road, there also exist blind corners for drivers traveling in and out of major drainages, which indicates that the road is not wide enough for others to pass by.

The project will include various new improvements along the roadway segment under study as summarized below:

• Construction of one improved low-water crossing made of a concrete slab on grade (near Boring B-1);

• Armoring inlets and outlets of existing galvanized steel pipe culverts with grouted riprap (near Borings B-1, B-2, and B-3);

• Road widening and chip seal placement to improve the Line-of-Sight distance on blind corners (near Boring B-4, Test Pits TP-1 & TP-2), with possible cut and fill earthwork;

• Construction of new drainage crossings with galvanized steel pipe culverts (near Test Pits TP-1 and TP-2).

Engineering plans for the proposed improvements were not available for our review at the time of our study. However, based on the provided information we understand that the construction of the new improvements will involve earthwork operations including grubbing and clearing, excavation of the existing soils, and new embankment fill placement. The earthwork cut and fills are assumed to be less than 5 feet deep and high; respectively.

6 FIELD EXPLORATION AND LABORATORY TESTING

On December 15th, 2022, Ninyo & Moore conducted a subsurface exploration at the site in order to evaluate the subsurface conditions and to collect soil samples for laboratory testing. Our evaluation consisted of the drilling, logging, and sampling of two test pits using manual excavation equipment and four exploratory borings using a CME 75 truck mounted drill rig equipped with hollow-stem augers (Figures 2A and 2B). The test pits extended to an approximate depth of 2 feet bgs, and the borings extended to approximate depths of 4.4 to 8.9

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 4 feet bgs. Each boring encountered formational material at depths ranging from roughly 3 to 6 feet bgs. Bulk and relatively undisturbed soil samples were collected at selected depth intervals in our borings.

Ninyo & Moore personnel logged the borings and test pits in general accordance with the

Unified Soil Classification System (USCS) and American Society for Testing and Materials

(ASTM) test method D 2488 by observing cuttings, drive (ring) samples and excavation spoils.

Collected ring samples were trimmed in the field, wrapped in plastic bags, and placed in cylindrical plastic containers to retain in-place moisture conditions. Similarly, Standard

Penetration Test (SPT) and bulk samples were sealed in plastic bags to retain their approximate in-place moisture. Detailed descriptions of the soils encountered are presented on the boring and test pit log in Appendix A.

The soil samples collected from our exploratory activities were transported to the Ninyo & Moore laboratory in Tucson, Arizona for geotechnical laboratory testing. The testing included in-situ moisture content and dry density, gradation, Atterberg limits, and corrosivity characteristics

(including pH, minimum electrical resistivity, and soluble sulfate and chloride contents). The results of the in-situ moisture content and dry density testing are presented on the boring and test pit logs in Appendix A and a description of each laboratory test method and the remainder of the test results are presented in Appendix B.

7 GEOLOGY AND SUBSURFACE CONDITIONS

The project site is located in the Transition Zone of the Basin and Range physiographic province, which is typified by broad alluvial valleys separated by steep, discontinuous, subparallel mountain ranges. The mountain ranges generally trend north-south and northwest-southeast. The basin floors consist of alluvium with thickness extending to several thousands of feet.

The basins and surrounding mountains were formed approximately 18 million years ago during the mid- to late-Tertiary age. Extensional tectonics resulted in the formation of horsts

(mountains) and grabens (basins) with vertical displacement along high-angle normal faults.

Intermittent volcanic activity also occurred during this time. The surrounding basins were filled with alluvium from the erosion of the surrounding mountains as well as from deposition from rivers. Coarser-grained alluvial material was deposited at the margins of the basins near the mountains.

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 5

The surficial geology of the site consists of native alluvium deposits underlain by Pliocene to

Middle Miocene (2 to 16 Ma) formational material consisting of moderately to strongly consolidated conglomerate and sandstone deposited on basin floors during and after late

Tertiary faulting. This formation includes lesser amounts of mudstone, siltstone, limestone and gypsum. These deposits are generally light gray or tan. They commonly form high rounded hills and ridges in modern basins, and locally form prominent bluffs. Deposits of this unit are exposed widely in the distressed basins of southeastern and central Arizona (Pearthree, Richard, Reynolds, Spencer, 2000).

Our review of the United States Department of Agriculture (USDA), Soil Conservation Service, Soil Survey of Graham County, indicates that the soils at this site are classified as different units as presented in Table 1. Loam is an agricultural soil classification that refers to a soil comprised of a mixture of clay, silt, and sand.

Table 1 – USDA Soil Units

UNIT NAME SOIL TYPES WITHIN UNIT PROFILE

Peloncillo Extremely cobbly sandy clay loam

Extremely cobbly sandy clay loam, very gravelly clay loam, cemented material

Peloncillo- Orthents -Pinaleno complex

Extremely cobbly sandy clay loam, very gravelly clay loam, cemented material

Cave gravelly sandy loam Gravelly sandy loam, cemented material

Continental- Pinaleno complex Gravelly sandy loam, gravelly clay loam, cobbly clay, gravelly clay, cemented material

7.1 Subsurface Conditions

Our knowledge of the subsurface conditions at the project site is based on our field exploration, laboratory testing, and our general understanding of the geology of the area. The following paragraphs provide a generalized description of the materials encountered. More detailed stratigraphic information is presented on the boring and test pit logs in Appendix A. The logs contain our field and laboratory test results, as well as our interpretation of conditions believed to exist between actual samples retrieved. Therefore, these logs contain both factual and interpretive information. Lines delineating subsurface strata on the logs are intended to group soils having similar engineering properties and characteristics. They should be considered approximate, as the actual transition between soil types (strata) may be gradual. A key to the soil symbols and terms used on the boring logs is provided in Appendix A.

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7.1.1 Roadway Pavement

Chip seal was encountered at the surface of our borings and was measured to be approximately 1-inch thick.

7.1.2 Alluvium/Residuum

Native alluvial and residual soils deposits were encountered beneath the chip seal in our borings, and at the surface of the test pits, and continued to the termination depth of test pits and formational material in our borings. In general, these deposits in our borings varied in relative density from medium dense to very dense, and consisted of poorly graded gravel with varying percentages of silt, clay and sand. Zones of cobbles, possible boulders, and carbonate cementation were encountered at various depths and locations.

7.1.3 Formational Material (Conglomerate)

Formational material consisting of Conglomerate was encountered below the alluvial and residual deposits in our borings. This formational material was encountered at depths ranging from 3 to 6 feet bgs and extended to the termination depths of approximately 4.4 to

8.9 feet bgs in our borings.

7.2 Groundwater

Groundwater was not encountered in our exploratory borings and test pits. Based on well data provided by the United State Geological Survey (USGS) monitoring location 325224109305001 within the general project area, groundwater has been historically measured at a depth on the order of 30 feet bgs. However, it should be noted that groundwater levels near the site can fluctuate due to seasonal variations, flows in the Gila River and other nearby washes, irrigation, groundwater withdrawal or injection, and other factors.

8 GEOLOGIC HAZARDS

The following section provides a discussion regarding potential geologic hazards such as land subsidence, earth fissures, faulting and seismicity.

8.1 Land Subsidence and Earth Fissures

Groundwater depletion, due to groundwater pumping, has caused land subsidence and earth fissures in numerous alluvial basins in Arizona. It has been estimated that subsidence has affected more than 3,000 square miles and has caused damage to a variety of engineered structures and agricultural land. From 1948 to 1983, excessive groundwater withdrawal has

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 7 been documented in several alluvial valleys where groundwater levels have been reportedly lowered by up to about 500 feet. With such large depletions of groundwater, the alluvium has undergone consolidation resulting in large areas of land subsidence (Schumann and Genualdi, 1986).

In Arizona, earth fissures are generally associated with land subsidence and pose an on-going geologic hazard. Earth fissures generally form near the margins of geomorphic basins where significant amounts of groundwater depletion have occurred. Reportedly, earth fissures have also formed due to tensional stress caused by differential subsidence of the unconsolidated alluvial materials over buried bedrock ridges and irregular bedrock surfaces (Schumann and

Genualdi, 1986).

Based on our field reconnaissance and review of the referenced material, there are no known earth fissures at the surface of the subject site. Based on fissure maps published by the Arizona

Geological Survey (AZGS, 2014), the closest reported unconfirmed earth fissures to the site are located approximately 35 miles to the southeast of the project site near the Town of Bowie.

However, the site is located within Upper Gila Land Subsidence Feature. The Envisat Satellite

Interferometric Synthetic Aperture Radar (InSAR) data that compared satellite passes between

February 24, 2017 and January 17, 2022 indicated that up to 4 centimeters (or approximately

1.6 inches) of subsidence has been measured in the project area within the last approximately

5 years. Historic subsidence may have also occurred prior to ADWR’s 2017 measurements.

Continued groundwater withdrawal in the area may result in subsidence and the formation of new fissures or the extension of existing fissures. While the future occurrence of land subsidence and earth fissures cannot accurately be predicted, these phenomena are not expected to be a constraint to the construction of this project.

8.2 Faulting and Seismicity

The site lies within the Sonoran zone, which is a relatively stable tectonic region located in southwestern Arizona, southeastern California, southern Nevada, and northern Mexico

(Euge et al., 1992). This zone is characterized by sparse seismicity and few Quaternary faults.

Based on our field observations and on our review of readily available published geologic maps and literature, there are no known active faults underlying the subject site or adjacent areas.

The closest known Quaternary fault to the site is the Buena Vista Fault Zone, located approximately 4 miles southwest of the site. The Buena Vista Fault Zone is situated along the southwestern piedmont of the Black Hills. The fault zone is a series of northeast-striking normal faults that extends to about 2.5 miles in length. The most recent movement along this fault was

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 8 approximately 750,000 years ago during the Middle to Late Quaternary. The slip-rate category of this fault is less than 0.2 millimeters per year (Pearthree, 1998). Seismic parameters recommended for the design of the proposed improvements are presented in Section 10.2.

9 CONCLUSIONS

Based on the results of our subsurface evaluation, laboratory testing, and data analysis, the proposed construction is feasible from a geotechnical standpoint, provided the recommendations of this report are incorporated into the design of the project, as appropriate.

Geotechnical considerations include the following:

• Near surface alluvial and residual soil deposits can generally be excavated or ripped using heavy-duty earthmoving or excavation equipment. However, zones of carbonate cementation and very dense, gravelly materials, and possible cobble/boulder deposits should be anticipated at variable depths, which may result in difficult and/or slower excavation rates. In addition, relatively shallow formational material (Conglomerate) should be anticipated at some locations and will call for more aggressive excavation techniques including blasting.

• Alluvial and residual soils of variable relative densities encountered in our borings may be compressible upon saturation and loading.

• Imported soils and soils generated from on-site excavation activities, that exhibit a relatively low plasticity index (PI) can generally be used for engineered fill. Based on the results of our study, many of the on-site soils will be suitable for re-use as engineered fill.

• Groundwater was not observed in our borings. Based on nearby well data, the regional groundwater table has been historically measured at depths on the order of 30 feet bgs.

However, groundwater levels near the site can fluctuate due to seasonal variations, flows in the Gila River, washes, irrigation, groundwater withdrawal or injection, and other factors. In general, groundwater is not expected to be a constraint to the design and construction of this project.

• No documented geologic hazards are present underlying or immediately adjacent to the site.

However, the site is located within the Upper Gila Land Subsidence Feature. The InSAR data that compared satellite passes between February 24, 2017 and January 17, 2022 indicated that up to 4 centimeters (or approximately 1.6 inches) of subsidence has been measured in the project area within the last approximately 5 years.

10 RECOMMENDATIONS

The following sections present our geotechnical recommendations for the project design and construction. If the proposed construction is changed from that discussed in this report

Ninyo & Moore should be contacted for additional recommendations.

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 9

10.1 Earthwork

The following sections provide our earthwork recommendations for this project. In general, the earthwork specifications contained in the Maricopa Association of Governments (MAG) Uniform

Standard Specifications and Details for Public Works Construction (Standard Specifications) as amended by Graham County are expected to apply unless specifically noted.

10.1.1 Site Preparation

Construction areas should be cleared of deleterious materials, if any are present, construction debris, vegetation, and any other material that might interfere with the performance or progress of the work. These materials should be disposed of at a legal dumpsite. Existing features that call for relocation or removal and extend below finished grade, if present, should be removed, and the resulting excavations backfilled with compacted engineered fill as discussed in this report.

10.1.2 Excavations

Our evaluation of the excavation characteristics of the on-site soils is based on the results of our exploratory excavations, site observations, and experience with similar soils.

Generally, excavation of the near-surface alluvial and residual materials can generally be accomplished using heavy-duty earthmoving equipment. However, zones of gravel and cobbles were encountered at a relatively shallow depth in our exploratory excavations. In addition, zones of carbonate cementation and Formational material (Conglomerate) should be anticipated. As such, some excavations may call for more aggressive excavation techniques (i.e. machinery equipped with ripping teeth, pneumatic hammering, etc.) or blasting. Specifically, we anticipate that more aggressive excavation techniques may be needed for the new pipe culvert installation (locations TP-1 and TP-2) and roadway widening at cut sections.

Equipment and procedures should be used that do not cause disturbance to the excavation bottoms. Excavators and backhoes with buckets having large claws to loosen the soil should be avoided when excavating the last 6 to 12 inches. Such equipment will probably disturb the excavation bases. If wet or saturated soils are encountered at the excavation bases, these soils may soften under the action of light equipment and foot traffic.

The contractor should provide safely sloped excavations or an adequately constructed and braced shoring system, in compliance with Occupational Safety and Health Administration

(OSHA) regulations, for employees working in an excavation that may expose them to the

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 10 danger of moving ground. For planning purposes and according to OSHA soil classifications, a "Type C" soil should be considered for this project for the alluvial and uncemented colluvial deposits. This corresponds to a temporary slope inclination no steeper than 1.5:1 (horizontal to vertical [H:V]). If material is stored or equipment is operated near an excavation, stronger shoring should be used to resist the extra pressure due to superimposed loads. During excavation, soil classification and excavation performance should be evaluated in the field by Ninyo & Moore in accordance with the

OSHA regulations.

10.1.3 Fill Materials and Reuse of On-site Soils

On-site and imported soils that exhibit relatively low plasticity indices and very low to low expansive potential are generally suitable for re-use as engineered fill. Relatively low plasticity indices are defined as a PI value of 15, or less, as evaluated by ASTM D 4318.

Based on laboratory test results, the shallow-depth (upper 5 feet) on-site soils are characterized by PI values ranging from 0 (non-plastic) to 10. As such, it is our opinion that many of the on-site soils will be suitable for re-use as engineered fill during construction.

The Contractor should perform additional testing prior to or during construction to better delineate the soil conditions at the site.

In addition, clay lumps, construction debris and soil/rock particles should not be larger than

4 inches in dimension. Any unsuitable material should be disposed of off-site or in non-structural areas.

Engineered fill materials in contact with ferrous metals should also have low corrosion potential (minimum resistivity more than 2,000 ohm-cm, chloride content less than 25 parts per million [ppm]). Engineered fill material in contact with concrete should have a soluble sulfate content of less than 0.1 percent.

10.1.4 Subgrade Preparation

As stated previously, the near-surface soils observed in our borings generally consisted of medium dense to very dense poorly graded gravel with variable percentages of silt, clay and sand, in our borings. Based on our field test results and experience with similar subsurface conditions, the near-surface alluvial and colluvial material may exhibit collapse potential upon saturation. Accordingly, we recommend that new fill embankments, grouted rip rap protection, slab-on-grade and pavements be supported on 6 inches of moisture-conditioned and compacted engineered fill, as measured from the bottom of the aggregate base (AB) course or leveling layer, where applicable. If competent bedrock is encountered

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 11 prior to a 6-inch depth, we should be notified. This can be achieved by overexcavation or in-place scarification. This subgrade improvement should extend laterally 1 foot beyond the new improvement footprint.

Engineered fill soils should be moisture-conditioned within 2 percent of the optimum and mechanically compacted to 95 percent of the maximum dry density as evaluate in accordance with ASTM D 698. Engineered fill should generally be placed in 8-inch-thick loose lifts such that each lift is firm and non-yielding under the weight of construction equipment.

An earthwork (shrinkage) factor of 5 to 15 percent is estimated. This shrinkage factor range represents an average of the material tested and assumes that materials excavated from the site will be placed as fill. Potential bidders should consider this in preparing estimates and should review the available data to make their own conclusions regarding excavation conditions.

10.1.5 New Embankment Fill

Based on the results of our study, many of the on-site alluvial/residual soils will be suitable for use in the new embankment construction. However, soil/rock particles larger than 4 inches in dimension should not be used for the new construction and screening of the material may be needed.

The new embankment fill should be placed in lifts the thickness of which will depend on the compaction equipment used, and should be re-compacted to 95 percent or more relative compaction, as evaluated by ASTM D 698 at a moisture content generally within 2 percent of the optimum moisture.

Settlements of the new embankment fills as recommended above should be anticipated and can generally be estimated to be on the order of 1 to 1-½ percent of the fill height. Due to the generally unsaturated and granular nature of the on-site soils majority of settlement is anticipated to occur during construction. No appreciable long-term settlements are anticipated.

Where new fill is to be placed on existing slopes, we recommend that horizontal benches angled slightly into the slope be cut into the native soils prior to placing fill. Benches should roughly parallel slope contours. These benches should extend 4 feet or more into competent material at vertical distances of approximately 4 feet. Bench recommendations may need revision during construction to account for field conditions

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 12

10.1.6 Permanent Slopes

Based on our experience with similar projects, we recommend that permanent cut slopes within native soils (alluvium and colluvium) be constructed no steeper than 2H:1V.

Permanent fill embankment slopes should be no steeper than 2. 5H:1V.

We also understand that the new culvert inlet/outlets will be protected with grouted rip rap placed on prepared subgrade with a geotextile liner placed below the rip-rap. The rip-rap toe down detail was not available for our review. However, we understand that the toe down depth will address potential scour or head cutting depth and be 2 feet or more.

Surface erosion may occur on unprotected embankments from runoff during rain events, and from burrowing animals. This can result in features such as gullies, boils, and burrow holes. These features can ultimately reduce the embankments stability post construction, and after significant rain events. As such, erosion protection is recommended for earthen slopes. We recommend the following treatments be considered:

o Provide rock mulch consisting of ¾-inch or greater aggregate applied to the surface of the embankment.

o Apply relatively dense shallow rooted vegetation to the surface of the embankment to reduce potential for erosion.

o Implement an animal control strategy to mitigate colonization of burrowing animals.

Fill slopes should be constructed in a manner such that the degree of compaction is achieved to the finished slope face (e.g., overfilling and cutting to grade). We recommend that the overfill width be 12 inches or more; however, the overfill width may vary depending on the fill soil properties, compaction equipment used, and other factors.

Other erosion protection techniques and measures designed for steeper slopes are described in Section 10.1.7. below.

10.1.7 Special Slope Erosion Control Techniques

We understand the permanent slopes within the project area will have a very similar inclination to the existing ones. The steep slope areas devoid of vegetation will continue to exhibit surficial sloughing and raveling unless their surface is stabilized, or otherwise protected. Possible alternatives of the erosion protection of steep slopes (steeper than

2H:1V), may include concrete lining, soil cement, gabion mattresses, rip-rap and grouted rip-rap, segmented concrete mats (e.g. Contech Armorflex® and Petraflex® Systems), or

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 13 permanent turf reinforcement mats with hydroseeding. Considering the site conditions and economic aspects, the last technique may be considered for this project.

Permanent Turf Reinforcement Mats (TRM) consist of either 100 percent synthetic components (e.g. North American Green’s P300 and P550) or a composite of synthetic and natural materials (e.g. North American Green’s SC250 and C350). They feature a durable structure to reinforce vegetation at the root and stem level and include a matrix filler material that provides erosion protection immediately after installation. Typically, they are installed in a one-step operation, over the prepared seedbed. The seeds should be applied using a hydraulic-type equipment to establish turf. TRM should be installed to provide a uniform mulch layer and effective erosion protection for seedbed.

10.2 Seismic Design Considerations

Design of the proposed improvements should be performed in accordance with the requirements of the governing jurisdictions and applicable building codes. Table 2 presents the seismic design parameters for the site in accordance with International Building Code (IBC) guidelines and adjusted maximum considered earthquake (MCE) spectral response acceleration parameters evaluated using the California’s Office of Statewide Health Planning and Development (OSHPD) Seismic Design Maps (web-based).

Table 2 – International Building Code Seismic Design Criteria

Site Coefficients and Spectral Response Acceleration Parameters Values

Site Class C

Site Coefficient, Fa 1.3

Site Coefficient, Fv 1.5

Mapped Spectral Response Acceleration at 0.2-second Period, Ss 0.251 g

Mapped Spectral Response Acceleration at 1.0-second Period, S1 0.08 g

Spectral Response Acceleration at 0.2-second Period Adjusted for Site Class, SMS

0.326 g

Spectral Response Acceleration at 1.0-second Period Adjusted for Site Class, SM1

0.12 g

Design Spectral Response Acceleration at 0.2-second Period, SDS 0.217 g

Design Spectral Response Acceleration at 1.0-second Period, SD1 0.08 g

10.3 Slab-On-Grade

The design of the slab-on-grade is the responsibility of the structural engineer. Placement of the reinforcement in the slab is vital for satisfactory performance. The slabs should be underlain by

4 or more inches of aggregate base material in general accordance with the Standard

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 14

Specifications. We recommend that the slab-on-grade be supported on engineered fill as described in this report.

Fill soils under slabs should be maintained in a moist condition until the overlying slab is constructed. Joints should be constructed at intervals designed by the structural engineer to help reduce random cracking of the slab.

10.4 Pavements

We understand a chip seal (or double chip seal) surfacing will be constructed for any new pavement for this project in accordance with Section 330 of the Standard Specifications. The subgrade soils should be prepared in accordance with this report.

10.5 Corrosion

The corrosion potential of the on-site materials was analyzed to evaluate its potential effect on the foundations and structures. Corrosion potential was evaluated using the results of laboratory testing of soil samples obtained during our subsurface evaluation that were considered representative of soils at the subject site.

Laboratory testing consisted of pH, minimum electrical resistivity, and chloride and soluble sulfate contents. The pH and minimum electrical resistivity tests were performed in general accordance with Arizona Test 236c, while sulfate and chloride tests were performed in accordance with Arizona Test 733 and 736, respectively. The results of the corrosivity tests are presented in Appendix B.

The soil pH value of the tested samples ranged between 8.0 and 8.2, which is considered to be alkaline. The minimum electrical resistivity measured in the laboratory varied between 1,005 and 2,745 ohm-cm, which is considered to be corrosive to ferrous metals. The chloride content of the samples tested varied between 10 and 21 parts per million (ppm), which is considered to represent a non-corrosive environment to ferrous metals. The soluble sulfate content of the soil samples tested ranged between approximately 0.005 and 0.034 percent by weight, which is considered to represent negligible sulfate exposure for concrete.

The results of the laboratory testing indicate that the on-site materials may be corrosive to ferrous materials. It is possible that soils with variable corrosivity characteristics may be encountered at the site and should be evaluated during construction. A corrosion specialist should be consulted for further recommendations.

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 15

10.6 Concrete

Laboratory chemical tests performed on on-site soil sample indicated sulfate content of about

0.005 and 0.034 percent by weight. Based on American Concrete Institute (ACI), the on-site soils should be considered to represent negligible sulfate exposure to concrete.

We recommend the use of Type II cement for construction of concrete structures at this site.

Due to potential uncertainties as to the use of reclaimed irrigation water, or topsoil that may contain higher sulfate contents, pozzolan or admixtures designed to increase sulfate resistance may be considered.

The concrete should have a water-cementitious materials ratio of no more than 0.50 by weight for normal weight aggregate concrete. The structural engineer should select the concrete design strength based on the project specific loading conditions. Higher strength concrete may be selected for increased durability and resistance to slab curling and shrinkage cracking.

We recommend that concrete cover over reinforcing steel for foundations be in accordance with the recommendations of the structural engineer. The structural engineer should be consulted for additional concrete specifications.

11 SITE DRAINAGE

Surface drainage should be provided to divert water away from the structures and off of paved surfaces. Surface water should not be permitted to drain toward the structures or to pond adjacent to footings or on flatwork or pavement areas. Positive drainage for this project is defined as a slope of 2 or more percent for a distance of 5 or more feet away from the structures.

12 CONSTRUCTION OBSERVATION AND TESTING

During construction operations, we recommend that Ninyo & Moore perform observation and testing services for the project. These services should be performed to evaluate exposed subgrade conditions, including the extent and depth of overexcavation, to evaluate the suitability of the on-site materials for use as fill, and to observe placement and test compaction of fill soils.

Qualified subcontractors utilizing appropriate techniques and construction materials should perform construction of the proposed improvements.

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 16

13 LIMITATIONS

The field evaluation, laboratory testing, and geotechnical analyses presented in this geotechnical report have been conducted in general accordance with current practice and the standard of care exercised by geotechnical consultants performing similar tasks in the project area. No warranty, expressed or implied, is made regarding the conclusions, recommendations, and opinions presented in this report. There is no evaluation detailed enough to reveal every subsurface condition. Variations may exist and conditions not observed or described in this report may be encountered during construction. Uncertainties relative to subsurface conditions can be reduced through additional subsurface exploration. Additional subsurface evaluation will be performed upon request. Please also note that our evaluation was limited to assessment of the geotechnical aspects of the project, and did not include evaluation of structural issues, environmental concerns, or the presence of hazardous materials.

This document is intended to be used only in its entirety. No portion of the document, by itself, is designed to completely represent any aspect of the project described herein. Ninyo & Moore should be contacted if the reader requires additional information or has questions regarding the content, interpretations presented, or completeness of this document.

This report is intended for design purposes only. It does not provide sufficient data to prepare an accurate bid by contractors. It is suggested that the bidders and their geotechnical consultant perform an independent evaluation of the subsurface conditions in the project areas. The independent evaluations may include, but not be limited to, review of other geotechnical reports prepared for the adjacent areas, site reconnaissance, and additional exploration and laboratory testing.

Our conclusions, recommendations, and opinions are based on an analysis of the observed site conditions. If geotechnical conditions different from those described in this report are encountered, our office should be notified and additional recommendations, if warranted, will be provided upon request. It should be understood that the conditions of a site could change with time as a result of natural processes or the activities of man at the subject site or nearby sites.

In addition, changes to the applicable laws, regulations, codes, and standards of practice may occur due to government action or the broadening of knowledge. The findings of this report may, therefore, be invalidated over time, in part or in whole, by changes over which Ninyo & Moore has no control.

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 17

This report is intended exclusively for use by the client. Any use or reuse of the findings, conclusions, and/or recommendations of this report by parties other than the client is undertaken at said parties’ sole risk.

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023 18

14 REFERENCES

American Association of State Highway and Transportation Officials, 1993, AASHTO Guide for Design of Pavement Structures.

American Concrete Institute, Guidelines for Concrete Floor and Slab Construction (ACI 302.1R).

American Concrete Institute, Guidelines for Residential Cast-in-Place Concrete Construction

(ACI 332R).

American Society for Testing and Materials (ASTM), Annual Book of ASTM Standards.

Google, Inc., Google Earth™ mapping service, http://earth.google.com.

International Code Council, 2018, International Building Code.

Nationwide Environmental Title Research (NETR), LLC, Historic Aerials by NETR Online, http://historicaerials.com/.

Ninyo & Moore, In-house proprietary information.

Occupational Safety and Health Administration (OSHA), Title 29 of the Code of Federal Regulations (CFR), Part No. 1926 - Safety and Health Regulations for Construction, Subpart P – Excavations.

Office of the State Engineer, Water Rights Division, https://www.ose.state.nm.us/WRAB/abstractMap.php

OSHPD Seismic Design Maps (web based).

United States Department of Agriculture (USDA), Soil Conservation Service, Soil Survey of Graham County, Arizona.

United States Geological Survey, Quaternary Fault and Fold Database of the United States, Interactive Fault Map, https://earthquake.usgs.gov/hazards/qfaults/.

United States Geological Survey (USGS), Water Resources Database, Gila River at Head of Safford Valley, https://waterdata.usgs.gov/monitoring-location/09448500/#parameterCode=00060&period=P30D

United States Geological Survey, 2021, Gila Box Quadrangle, Arizona – Graham County 7.5 Minute Series (Topographic): Scale 1:24,000 http://earth.google.com/ http://historicaerials.com/ https://www.ose.state.nm.us/WRAB/abstractMap.php https://earthquake.usgs.gov/hazards/qfaults/ https://waterdata.usgs.gov/monitoring-location/09448500/#parameterCode=00060&period=P30D https://waterdata.usgs.gov/monitoring-location/09448500/#parameterCode=00060&period=P30D

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023

Appendix A

Photographic Documentation

FIGURES

SITE

SITE SEE FIGURE 2B

SEE FIGURE 2A

Geotechnical & Environmental Sciences Consultants

1_

SL

.d w g

1/

B

SM

SITE LOCATION

FIGURE 1

NOTE: DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE. I REFERENCE: USGS, 2021. 0

FEET

2,000 4,000

BONITA CREEK ROADWAY IMPROVEMENTS

GRAHAM COUNTY, ARIZONA

607468001 I 01/23

N

B-3

B-2

B-1

Geotechnical & Environmental Sciences Consultants

EXPLORATION LOCATIONS

FEET

1_

SP

.d w g

1/

B

SM

400 8000

LEGEND

BONITA CREEK ROADWAY IMPROVEMENTS

GRAHAM COUNTY, ARIZONA

607468001 I 01/23

FIGURE 2A

N

BORING

NOTE: DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE. I REFERENCE: GOOGLE EARTH 2023.

B-3

B-4

DRY

CANYON

SPRING

CANYON

TP-1

TP-2

Geotechnical & Environmental Sciences Consultants

EXPLORATION LOCATIONS

FEET

1_

SP

2.

dw g

1/

B

SM

400 8000

LEGEND

BONITA CREEK ROADWAY IMPROVEMENTS

GRAHAM COUNTY, ARIZONA

607468001 I 01/23

FIGURE 2B

N

NOTE: DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE. I REFERENCE: GOOGLE EARTH 2023.

BORINGB-4

TEST PITTP-2

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023

APPENDIX A

Boring and Test Pit Logs

Ninyo & Moore | Bonita Creek Roadway Improvements, Graham County, Arizona | 607468001 | January 12, 2023

APPENDIX A

BORING AND TEST PIT LOGS

Field Procedure for the Collection of Disturbed Samples Disturbed soil samples were obtained in the field using the following methods.

Bulk Samples Bulk samples of representative earth materials were obtained from the exploratory borings and test pits. The samples were bagged and transported to the laboratory for testing.

The Standard Penetration Test (SPT) Sampler Disturbed drive samples of earth materials were obtained by means of a Standard Penetration Test sampler. The sampler is composed of a split barrel with an external diameter of 2 inches and an unlined internal diameter of 1-3/8 inches. The sampler was driven into the ground 12 to 18 inches with a 140-pound hammer falling freely from a height of 30 inches in general accordance with ASTM D 1586. The blow counts were recorded for every 6 inches of penetration; the blow counts reported on the log are those for the last 12 inches of penetration. Soil samples were observed and removed from the sampler, bagged, sealed and transported to the laboratory for testing.

Field Procedure for the Collection of Relatively Undisturbed Samples Relatively undisturbed soil samples were obtained in the field using the following methods.

The Modified Split-Barrel Drive Sampler The sampler, with an external diameter of 3.0 inches, was lined with 1-inch long, thin brass rings with inside diameters of approximately 2.4 inches. The sample barrel was driven into the ground with the weight of a hammer or the Kelly bar of the drill rig in general accordance with ASTM D 3550. The driving weight was permitted to fall freely. The approximate length of the fall, the weight of the hammer or bar, and the number of blows per foot of driving are presented on the boring log as an index to the relative resistance of the materials sampled. The samples were removed from the sample barrel in the brass rings, sealed, and transported to the laboratory for testing.

ASTM D 2488

COARSE-

SOILS

more than

50% retained on No. 200 sieve

GRAVEL

more than

50% of coarse fraction retained on No. 4 sieve

CLEAN GRAVEL GW well-graded GRAVEL

GP poorly graded GRAVEL

GRAVEL with

DUAL

CLASSIFICATIONS

GW-GM well-graded GRAVEL with silt

GP-GM poorly graded GRAVEL with silt

GW-GC well-graded GRAVEL with clay

GP-GC poorly graded GRAVEL with

GRAVEL with

FINES

more than

GM silty GRAVEL

GC clayey GRAVEL

GC-GM silty, clayey GRAVEL

50% or more of coarse fraction passes

No. 4 sieve

CLEAN SAND SW well-graded SAND

SP poorly graded SAND

SAND with

DUAL

CLASSIFICATIONS

SW-SM well-graded SAND with silt

SP-SM poorly graded SAND with silt

SW-SC well-graded SAND with clay

SP-SC poorly graded SAND with clay

SAND with FINES more than

SM silty SAND

SC clayey SAND

SC-SM silty, clayey SAND

SOILS

50% or more passes No. 200 sieve

CLAY

liquid limit less than 50%

INORGANIC

CL lean CLAY

ML SILT

CL-ML silty CLAY

ORGANIC

OL (PI > 4) organic CLAY

OL (PI < 4) organic SILT

CLAY

liquid limit

50% or more

INORGANIC

CH fat CLAY

MH elastic SILT

ORGANIC

OH (plots on or above “A”-line) organic CLAY

OH (plots below “A”-line) organic SILT

Highly Organic Soils PT Peat

Very Loose < 4 < 8 < 3 < 5

Loose 5 - 10 9 - 21 4 - 7 6 - 14

Medium Dense 11 - 30 22 - 63 8 - 20 15 - 42

Dense 31 - 50 64 - 105 21 - 33 43 - 70

Very Dense > 50 > 105 > 33 > 70

Very Soft < 2 < 3 < 1 < 2

Soft 2 - 4 3 - 5 1 - 3 2 - 3

Firm 5 - 8 6 - 10 4 - 5 4 - 6

9 - 15…